Teen Moon: Moon Ooze

Overview

Children model how the Moon's volcanic period reshaped its earlier features. The children consider that the broad, shallow impact basins — which had formed earlier while it was a "kid Moon" — contained cracks through which magma seeped up. A plate in which slits have been cut is used to represent an impact basin and a dish of red-colored water is used to represent the pockets of magma within the Moon's upper layers. When the model impact basin is pressed into the "magma," "lava" fills in the low areas through the same process that produced the dark patches, or maria, on the Moon.Children may examine a type of Earth rock (named basalt) that is also found on the Moon and that would have been shaped by the processes explored here.This station investigates the Moon's "teen years," when it was one to threebillion years old.

What's the Point?

Scientists study the Moon's rocks and surface features to learn how it formed and changed over its long "lifetime."

The Moon was still warm enough 3.0 and 3.8 billion years ago to have volcanic activity.

Magma poured out through cracks in the lunar surface — many of which were created by the earlier impacts — and flooded across the lowest regions on the lunar surface to create the maria.

The lava quickly crystallized to form the large, smooth, dark regions we see on the Moon, called "lunar maria" by early astronomers after the Latin name for "seas," as these areas looked like seas to early astronomers.

Maria are made of a fine-grained, dark, volcanic rock called basalt — the same rock type as found on Earth's ocean floors and the same type that makes up the islands of Hawaii.

The Moon has some of the same types of rocks that are found on Earth. The rocks have certain properties, such as color.

Models — such as those the children are using here — can be tools for understanding the natural world.

Materials

The following materials are for one Teen Moon: Moon Ooze activity set and will serve approximately 10 children working in teams of two to three.
Two sets are recommended for a station:

Optional: butcher paper, newspapers, or disposable table cloths for the activity area

Preparation

This is a fun, but messy activity! If possible, tell the children ahead of time to wear an old shirt or apron, or you may wish to provide trash bags for them to wear. Have a towel handy for cleaning spills.

Cover the table with butcher paper, newspapers, or disposable table cloths, if desired.

Prepare one of the plates to serve as a model of an impact basin: Cut three long slices along the bottom of the plastic plate with a utility knife.(Note that plates larger than about 6 inches wide become flimsy when cut and do not work for this activity.) The other plate should remain uncut and will be used to hold the red-colored water during the activity.

Mix the food coloring with some water in a small (1 cup-sized or so) container with a pour spout. Provide a medicine dropper (or an eye dropper or turkey baster) for the children to use to pour a little of the water into a plate.

After each team has had a their turn, reset the station by removing the slit plate (the model “impact basin”) from the water and wiping it dry.

Place the Earth rock sample, art materials, Moon map, and children’s guide at the station.

Activity

Conclusion

Once they have completed the experiment, the children should understand that the large, smooth, dark regions we see on the Moon formed billions of years ago when lava oozed through cracks in the lunar basins. The lava filled in earlier impact basins and solidified. Because the lava is younger than the light-colored regions, it is less cratered and looks smooth. Early astronomers mistook their smooth appearance for seas, and called the Moon's dark regions "maria" after the Latin word for "seas."

A Little Background for the Facilitator

The "teen" Moon bore the scars of an earlier period of intense bombardment, which left behind large, cracked basins across its face. While cool on the outside, portions of the Moon's interior were still hot, heated by radioactive decay of unstable isotopes of elements, such as uranium and thorium, and the processes of accretion and differentiation. Isolated pockets of hot mantle material slowly rose to the surface, melting at lower pressures. This magma poured out through cracks in the lunar surface — fissures — many of which were created by the earlier impacts. The magma flooded across the lowest regions on the lunar surface to fill the impact basins. It crystallized quickly, forming basalt, a dark, fine-grained, volcanic rock. The large, smooth, dark regions we see on the Moon are the basaltic "lunar maria." "Maria" is Latin for "seas," as these areas looked like seas to early astronomers. They are smooth because they are less cratered than the lunar highlands. The smaller number of craters in the maria suggests that these regions have not been impacted as much and therefore are younger. Mare basalts have been radiometrically dated to be between 3.0 and 3.8 billion years old.

Imagine standing on the Moon at this time. Hot basalt lava flowed from long fissures, filling regions of low elevation. Fountains of lava sporadically erupted along the fissures, spewing molten rock high above the lunar surface. Chilled magma droplets fell back as beads of colored volcanic glass, later sampled by Apollo astronauts. Flowing lava cut channels into the landscape. In a few locations, small volcanic domes built up on the surface of the maria. Gradually, as the Moon’s interior cooled, volcanism ceased. Lunar volcanism decreased significantly by 3 billion years ago and ceased completely by about 1 billion years ago as the interior cooled.